Analog front end circuit for touch controller and operating method thereof

ABSTRACT

An analog front-end circuit for a touch controller and an operating method thereof are provided. The analog front-end circuit includes an analog front-end, a first switch and a second switch. The analog front-end includes an input terminal and an output terminal. The first switch includes a first terminal and a second terminal. The first terminal of the first switch is coupled to the input terminal of the analog front-end, and the second terminal of the first switch is coupled to a panel routing. The second switch includes a first terminal and a second terminal. The first terminal of the second switch is coupled to the second terminal of the first switch, and the second terminal of the second switch is coupled to a reference voltage.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part application of and claims thepriority benefit of a prior application Ser. No. 16/897,290, filed onJun. 10, 2020, which claims the priority benefit of U.S. provisionalapplication Ser. No. 62/976,299, filed on Feb. 13, 2020. Thisapplication also claims the priority benefit of Taiwan applicationserial no. 109143649, filed on Dec. 10, 2020. The entirety of theabove-mentioned patent application is hereby incorporated by referenceherein and made a part of this specification.

BACKGROUND Technical Field

The disclosure generally relates to a function circuit in a touchcontroller, in particular, to an analog front-end circuit for touchcontroller and an operating method thereof.

Description of Related Art

Referring to FIG. 1, the conventional analog front-end circuit 100 for ageneral touch controller may include, for example, an amplifier 101, acapacitor 102 and a resistor 103. The capacitor 102 and the resistor 103are respectively coupled between an inverting input terminal and anoutput terminal of the amplifier 101. For the general touch controller,the conventional analog front-end circuit 100 may be configured toreceive a touch signal provided by a touch sensor through the invertinginput terminal of the amplifier 101, and receive a reference voltagethrough a non-inverting input terminal of the amplifier 101. Thus, theamplifier 101 may output an output signal according to the touch signaland the reference voltage. However, if the touch controller is used forreceiving the touch signal from a display touch module having a displaypanel and a touch panel, the amplifier 101 may receive the touch signalprovided by the touch panel with coupling noise signals from the displaypanel. In other words, the output signal outputted by the amplifier 101may have signal distortion problems causing by the coupling noisesignals from the display panel, thus may further render the analogfront-end circuit 100 to be ineffective. Therefore, regarding how todesign a new analog front-end circuit having a signal-to-noise ratio,solutions of several embodiments are provided below.

SUMMARY

The disclosure is directed to an analog front-end circuit for a touchcontroller and an operating method thereof capable of providingeffective touch sensing function.

The analog front-end circuit for a touch controller of an embodiment ofthe disclosure includes an analog front-end, a first switch and a secondswitch. The analog front-end includes an input terminal and an outputterminal. The first switch includes a first terminal and a secondterminal. The first terminal of the first switch is coupled to the inputterminal of the analog front-end and the second terminal of the firstswitch is coupled to the panel routing. The second switch includes afirst terminal and a second terminal. The first terminal of the secondswitch is coupled to the second terminal of the first switch and thesecond terminal of the second switch is coupled to a reference voltage.

The operating method of another embodiment of the disclosure is adaptedto an analog front-end circuit for a touch controller. The analogfront-end circuit includes an analog front-end, a first switch and asecond switch. An input terminal of the analog front-end is coupled to afirst terminal of the first switch. A second terminal of the firstswitch is coupled to a panel routing and a first terminal of the secondswitch. A second terminal of the second switch is coupled to a referencevoltage. The panel routing is further coupled to a touch panel and adisplay panel. The operating method includes following steps: turning onthe second switch during a first period; transmitting a coupling noisesignal from the display panel through the panel routing and the secondswitch to the reference voltage during the first period; turning on thefirst switch during a second period; and receiving a touch drivingsignal of the touch panel by the input terminal of the analog front-endthrough the panel routing and the first switch during the second period.The first period and the second period are non-overlapping.

Based on the above, according to the analog front-end circuit for thetouch controller and the operating method thereof of the disclosure, theanalog front-end circuit can effectively avoid or reduce to receive thenoise signal generated by the display panel when the analog front-endcircuit receives the touch driving signal.

To make the aforementioned more comprehensible, several embodimentsaccompanied with drawings are described in detail as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of this specification. The drawings illustrate exemplaryembodiments of the disclosure and, together with the description, serveto explain the principles of the disclosure.

FIG. 1 is a schematic diagram illustrating a conventional analogfront-end circuit.

FIG. 2 is a schematic diagram illustrating a touch display moduleaccording to an embodiment of the disclosure.

FIG. 3A is a schematic diagram illustrating an analog front-end circuitadapted to the mutual capacitance touch panel according to an embodimentof the disclosure.

FIG. 3B is a schematic diagram illustrating an analog front-end circuitadapted to the self-capacitance touch panel according to an embodimentof the disclosure.

FIG. 4 is a signal waveform diagram illustrating the operation of theanalog front-end circuit according to an embodiment of the disclosure.

FIG. 5A is a schematic diagram illustrating an analog front-end circuitadapted to the mutual capacitance touch panel according to anotherembodiment of the disclosure.

FIG. 5B is a schematic diagram illustrating an analog front-end circuitadapted to the self-capacitance touch panel according to anotherembodiment of the disclosure.

FIG. 6 is a signal waveform diagram illustrating the operation of theanalog front-end circuit according to another embodiment of thedisclosure.

FIG. 7 is a signal waveform diagram illustrating the operation of theanalog front-end circuit according to yet another embodiment of thedisclosure.

FIG. 8 is a signal waveform diagram illustrating the operation of theanalog front-end circuit according to yet again another embodiment ofthe disclosure.

FIG. 9 is a flowchart of an operating method according to an embodimentof the disclosure.

DESCRIPTION OF THE EMBODIMENTS

It is to be understood that other embodiments may be utilized andstructural changes may be made without departing from the scope of thedisclosure. Also, it is to be understood that the phraseology andterminology used herein are for the purpose of description and shouldnot be regarded as limiting. The use of “including,” “comprising,” or“having” and variations thereof herein is meant to encompass the itemslisted thereafter and equivalents thereof as well as additional items.Unless limited otherwise, the terms “connected,” “coupled,” and“mounted,” and variations thereof herein are used broadly and encompassdirect and indirect connections, couplings, and mountings.

FIG. 2 is a schematic diagram illustrating a touch display moduleaccording to an embodiment of the disclosure. Referring to FIG. 2, thetouch display module 200 of the disclosure includes a touch panel 210and a display panel 220, and the touch panel 210 is disposed on thedisplay panel 220. In the embodiment of the disclosure, the touch panel210 includes a plurality of touch sensors arranged in an array. In theembodiment of the disclosure, the touch panel 210 may be a mutualcapacitance touch panel or a self-capacitance touch panel. The displaypanel 220 may be a light-emitting diode (LED) display panel, a micro LEDdisplay panel, an organic light-emitting diode (OLED) display panel, aliquid-crystal display (LCD) panel or other types of display panels, andincludes a plurality of pixel units arranged in an array. The pixelunits of the display panel 220 are driven by a plurality gate lines GSand a plurality of source lines SL, wherein the source lines SL may befurther coupled to multiplexers 221, 222. The multiplexers 221, 222 mayrespectively be coupled to respective two source lines, and configuredto respectively and alternately drive the respective two source lines.

In the embodiment of the disclosure, each of the pixel units of thedisplay panel 220 may like a pixel unit 230 shown in FIG. 2. The pixelunit 230 includes transistors 231, 232, a light-emitting unit 233 and acapacitor 234. A first terminal of the transistor 231 is coupled to ahigh level power supply voltage ELVDD, and a second terminal of thetransistor 231 is coupled to a first terminal of the transistor 232. Asecond terminal of the transistor 232 is coupled to a first terminal ofthe light-emitting unit 233, and a second terminal of the light-emittingunit 233 is coupled to a low level power supply voltage ELVSS. Thecapacitor 234 is coupled between the high level power supply voltageELVDD and a control terminal of the transistor 231. In the embodiment ofthe disclosure, a control terminal of the transistor 232 is configuredto receive an emission signal ES and drive the light-emitting unit 233according to the emission signal ES.

FIG. 3A is a schematic diagram illustrating an analog front-end circuitadapted to the mutual capacitance touch panel according to an embodimentof the disclosure. Referring to FIG. 3, the analog front-end circuit 300may be disposed in a touch controller for receiving a touch drivingsignal TS from a sense capacitance (for example, mutual inductancecapacitance) of the touch panel 210 of FIG. 2, and the touch controllermay further include other function circuits, such as display driver fordriving the display panel 220 of FIG. 2. In the embodiment of thedisclosure, the analog front-end circuit 300 includes an analogfront-end 310, a first switch 320 and a second switch 330. The analogfront-end 310 includes an input terminal and an output terminal. Thefirst switch 320 includes a first terminal and a second terminal. Thefirst terminal of the first switch 320 is coupled to the input terminalof the analog front-end 310, and the second terminal of the first switchis coupled to a panel routing L1, wherein the panel routing L1 has anequivalent resistance 340. The second switch 330 includes a firstterminal and a second terminal. The first terminal of the second switch330 is coupled to the second terminal of the first switch 320, and thesecond terminal of the second switch 330 is coupled to a referencevoltage Vf. In another embodiment of the disclosure, the referencevoltage Vf may be a common mode voltage. Additionally, the analogfront-end 310 of the disclosure is a signal processing circuit. Theanalog front-end 310 may further include other circuit units or otherfunction circuits, such as the analog front-end circuit 100 of FIG. 1,but the disclosure is not limited thereto.

It should be noted that, the touch controller described in eachembodiment of the disclosure may be integrated in a composite chip witha display driver, such as a touch and display driver integration (TDDI)chip. Alternatively, the touch controller described in each embodimentof the disclosure may be integrated in a composite chip with afingerprint sensor driver and a display driver, such as a fingerprint,touch and display driver integration (FTDI) chip.

Referring to FIG. 2 and FIG. 3A, in the embodiment of the disclosure,the analog front-end circuit 300 may be coupled to the touch panel 210through the panel routing L1, and there is an equivalent capacitance 350between the panel routing L1 and the touch panel 210. One terminal ofthe equivalent capacitance 350 may be coupled to the equivalent resistor340 and the panel routing L1, and another one terminal of the equivalentcapacitance 350 may be coupled to the touch panel 210 through the nodeA1. However, owing to the touch panel 210 is integrated with the displaypanel 220, the analog front-end circuit 300 may also be coupled to thedisplay panel 220 through the panel routing L1, wherein there is anequivalent capacitance 360 between the panel routing L1 and the displaypanel 220. One terminal of the equivalent capacitance 360 may be coupledto the equivalent resistor 340 and the panel routing L1, and another oneterminal of the equivalent capacitance 360 may be coupled to the displaypanel 220 through the node A2. In the embodiment of the disclosure, theanalog front-end 310 is configured to receive a touch driving signal TSfrom a touch sensor of the touch panel 210 through the panel routing L1and the first switch 320 to the input terminal of the analog front-end310 when the first switch 320 is turned on and the second switch 330 isturned off, so that the output terminal of the analog front-end 310outputs an output voltage Vout1 according to the touch driving signalTS. Further, the analog front-end circuit 300 is further configured totransmit a coupling noise signal NS from the display panel 220 throughthe panel routing L1 and the second switch 330 to the reference voltageVf when the second switch 330 is turned on and the first switch 320 isturned off. In other words, the analog front-end circuit 300 may preventthe analog front-end 310 from receiving the coupling noise signal NSfrom the display panel 220 by controlling the conduction states of thefirst switch 320 and the second switch 330. In addition, in oneembodiment, the coupling noise signal NS may also include theinterference signal provided by the fingerprint sensor.

FIG. 3B is a schematic diagram illustrating an analog front-end circuitadapted to the self-capacitance touch panel according to an embodimentof the disclosure. Referring to FIG. 3B, the analog front-end circuit500 may be disposed in the touch controller to send the touch drivingsignal TS to the touch panel 210 of FIG. 2 to sense the sensecapacitance (for example, a self-capacitance) of the touch panel 210,and the touch controller may further include other functional circuits,such as a display driver for driving the display panel 220 of FIG. 2. Inthe embodiment of the disclosure, the analog front-end circuit 500includes an analog front-end 510, a first switch 520, and a secondswitch 530. The analog front end 510 includes a first input terminal, asecond input terminal, and an output terminal. The first input terminalof the analog front end 510 is coupled to the output terminal of theanalog front end 510. The first switch 520 includes a first terminal anda second terminal. The first terminal of the first switch 520 is coupledto the first input terminal of the analog front end 510, and the secondterminal of the first switch 520 is coupled to the panel routing L3,where the panel routing L3 has an equivalent resistance 540. The secondswitch 530 includes a first terminal and a second terminal. The firstterminal of the second switch 530 is coupled to the second terminal ofthe first switch 520, and the second terminal of the second switch 530is coupled to the reference voltage Vf1. In another embodiment of thedisclosure, the reference voltage Vf1 may be the touch driving signal TSor a common mode voltage, but the disclosure is not limited thereto. Inaddition, the analog front end 510 of the disclosure is a signalprocessing circuit. The analog front end 510 may further include othercircuit units or other functional circuits, such as the analog front endcircuit 100 shown in FIG. 1, but the disclosure is not limited thereto.

Referring to FIG. 2 and FIG. 3B, in the embodiment of the disclosure,the analog front-end circuit 500 may be coupled to the touch panel 210through the panel routing L3 and the node A3. Since the touch panel 210and the display panel 220 are integrated, the analog front-end circuit500 may also be coupled to the display panel 220 through the panelrouting L3, where an equivalent capacitance 560 exists between the panelrouting L3 and the display panel 220. One terminal of the equivalentcapacitance 560 may be coupled to the equivalent resistor 540 and thepanel routing L3, and another one terminal of the equivalent capacitance560 may be coupled to the display panel 220 through the node A4. In theembodiment of the disclosure, the analog front end 510 is configured toreceive the touch driving signal TS from the second input terminal ofthe analog front end 510 when the first switch 520 is turned on and thesecond switch 530 is turned off, and then transmit the touch drivingsignal TS to the touch sensor of the touch panel 210 through the firstinput terminal of the analog front end 510, the first switch 520, thepanel routing L3, and the node A3. The output terminal of the analogfront end 510 outputs the output signal Vout1 according to the touchdriving signal TS induced by the voltage change of self-capacitanceinduction. In addition, the analog front-end circuit 500 is further usedto transmit the coupling noise signal NS from the display panel 220 tothe reference voltage Vf1 through the panel routing L3 and the secondswitch 530 when the second switch 530 is turned on and the first switch520 is turned off. In other words, the analog front-end circuit 500 mayprevent the analog front-end 510 from receiving the coupling noisesignal NS by controlling the conduction state of the first switch 520and the second switch 530.

FIG. 4 is a signal waveform diagram illustrating the operation of theanalog front-end circuit according to an embodiment of the disclosure.Referring to FIG. 2, FIG. 3A and FIG. 4, the signal waveform of FIG. 4may be applied to the analog front-end circuit 300 of FIG. 3A. In theembodiment of the disclosure, the display panel 220 may be driven by ahorizontal sync signal HS, therefore the display panel 220 maysynchronously generate the coupling noise signal NS to the analogfront-end circuit 300. As shown in FIG. 4, each rising edge and eachfalling edge of the coupling noise signal NS may be synchronized witheach rising edge of the horizontal sync signal HS. In the embodiment ofthe disclosure, a signal period of the horizontal sync signal HS issynchronized with an alternating period of each adjacent rising edge andfalling edge of the touch driving signal TS, and the touch drivingsignal TS is shifted to prevent the analog front-end 310 from receivingthe coupling noise signal NS during the period of the analog front-end310 receiving the touch driving signal TS.

In the embodiment of the disclosure, the first switch 320 is configuredto receive a first switching signal S1, and the second switch 330 isconfigured to receive a second switching signal S2. The first switchingsignal S1 and the second switching signal S2 are periodic square waves,and the first switching signal S1 and the second switching signal S2 areinverted. Thus, the second switch 330 is turned on during first periodsP1, P1′, and the first switch 320 is turned on during second periods P2,P2′. The first period P1 and the second period P2 are non-overlapping,and the first period P1′ and the second period P2′ are non-overlapping.It is should be noted that, as shown in FIG. 4, each falling edge of thefirst switching signal S1 is synchronized with the each rising edge ofthe horizontal sync signal HS and the each falling edge and the eachrising edge of the coupling noise signal NS, and each rising edge of thefirst switching signal S1 is synchronized with the each rising edge andeach falling edge of the touch driving signal TS. Thus, each rising edgeof the second switching signal S2 is synchronized with the each risingedge of the horizontal sync signal HS and the each falling edge and theeach rising edge of the coupling noise signal NS, and each falling edgeof the second switching signal S2 is synchronized with the each risingedge and the each falling edge of the touch driving signal TS. In otherwords, when the coupling noise signal NS is transmitted through thepanel routing L1, the first switch 320 is turned off to prevent theanalog front-end 310 from receiving the coupling noise signal NS.

Therefore, as shown in FIG. 4, the analog front-end circuit 300 mayrelease the coupling noise signal NS through the panel routing L1 andthe second switch 330 to the reference voltage Vf during the firstperiods P1, P1′, and the analog front-end 310 is configured to receivethe touch driving signal TS through the panel routing L1 and the firstswitch 320 during the second period P2. The analog front-end 310 isconfigured to receive the touch driving signal TS without the couplingnoise signal NS or with a relatively low coupling noise signal NS duringthe second period P2, so that the output terminal of the analogfront-end 310 outputs an output signal Vout1 having voltage Va as shownin FIG. 4 during the second period P2. In the embodiment of thedisclosure, the analog front-end 310 may continuously output the outputsignal Vout1 having voltage Va during a next first period P1′, and theanalog front-end 310 may be reset (or discharged) during a next secondperiod P2′. It is should be noted that, the output signal Vout1 mayrepresent the touch information of the touch sensor of the touch panel210, wherein the output signal Vout1 may swing between the voltages 0 toVa during the periods P1 to P2′. In other words, the analog front-endcircuit 300 may be operated according to the signal waveform diagram ofFIG. 4, so that the analog front-end circuit 300 can output the outputsignal Vout1 having higher signal-to-noise ratio during the secondperiod P2.

Referring to FIG. 2, FIG. 3B and FIG. 4, the signal waveform of FIG. 4may also be applied to the analog front-end circuit 500 of FIG. 3B. Inthe embodiment of the disclosure, the display panel 220 may be driven bythe horizontal synchronization signal HS, so the display panel 220 maysynchronously generate the coupling noise signal NS which is transmittedto the analog front-end circuit 500. In the embodiment of thedisclosure, when the coupling noise signal NS is transmitted through thepanel routing L3, the first switch 520 is turned off to prevent thefirst end of the analog front end 510 from receiving the coupling noisesignal NS. As shown in FIG. 4, the analog front end circuit 500 mayrelease the coupling noise signal NS to the reference voltage Vf1through the panel routing L3 and the second switch 530 during the firstperiod P1, P1′, and the second output terminal of the analog front end510 is configured to receive the touch driving signal TS during thesecond period P2, so that the first output terminal of the analog frontend 510 is configured to transmit the touch driving signal TS throughthe first switch 520, the panel wiring L3 and the node A3 to the touchpanel 210 during the second period P2.

In the embodiment of the disclosure, the first terminal of the analogfront end 510 is configured to transmit the touch driving signal TS tothe touch panel 210 for sensing during the second period P2 withoutreceiving coupling noise signal NS or receiving relatively low couplingnoise signal NS, so that the output terminal of the analog front end 510outputs the output signal Vout1 having the voltage Va during the secondperiod P2. For example, the voltage Va is lower than the power supplyvoltage VDD. In the embodiment of the disclosure, the analog front end510 may continuously output the output signal Vout1 with the voltage Vaduring the next first period P1′, and may reset (or discharge) theanalog front end 510 during the next second period P2′. It should benoted that, the output signal Vout1 may represent the touch informationof the touch sensor of the touch panel 210, where the output signalVout1 may swing from the voltage 0 to the voltage Va during the periodP1 to the period P2′. In other words, the analog front-end circuit 500may operate according to the signal waveform diagram of FIG. 4, so thatthe analog front-end circuit 500 may output the output signal Vout1 witha higher signal-to-noise ratio during the second period P2.

However, regarding the signal waveform characteristics of the presentembodiment (FIG. 3B and FIG. 4), please refer to the above-mentionedembodiment (FIG. 3A and FIG. 4) to obtain sufficient teaching,suggestion, and implementation description, so there will not repeatagain. In addition, FIG. 3A and FIG. 3B may have different voltageoscillations when the signal waveform of FIG. 4 is applied. The signalwaveform of FIG. 4 is only used to show the relationships between theon-off switching results and the change of each signal waveform, and donot limit the analog front-end circuit 300 of FIG. 3A and the analogfront-end circuit 500 of FIG. 3B to operate with the same voltageamplitude results.

FIG. 5A is a schematic diagram illustrating an analog front-end circuitadapted to the mutual capacitance touch panel according to anotherembodiment of the disclosure. Referring to FIG. 5A, the analog front-endcircuit 400 may be disposed in a touch controller for receiving a touchdriving signal TS from a sense capacitance (for example, mutualinductance capacitance) of the touch panel 210 of FIG. 2, and the touchcontroller may further include other function circuits, such as displaydriver for driving the display panel 220 of FIG. 2. In the embodiment ofthe disclosure, the analog front-end circuit 400 includes an analogfront-end 410, a first switch 420, a second switch 430 and third switch470. In the embodiment of the disclosure, the analog front-end 410includes an input terminal and an output terminal. The first switch 420includes a first terminal and a second terminal. The first terminal ofthe first switch 420 is coupled to the input terminal of the analogfront-end 410, and the second terminal of the first switch is coupled toa panel routing L2, wherein the panel routing L2 has an equivalentresistance 440. The second switch 430 includes a first terminal and asecond terminal. The first terminal of the second switch 430 is coupledto the second terminal of the first switch 420, and the second terminalof the second switch 430 is coupled to a reference voltage Vf. The thirdswitch 470 includes a first terminal and a second terminal. The firstterminal of the third switch 470 is coupled to the input terminal of theanalog front-end 410 and the second terminal of the third switch 470 iscoupled to the output terminal of the analog front-end 410. In theembodiment of the disclosure, the third switch 470 is switchedsynchronously with the second switch 430. Additionally, the analogfront-end 410 of the disclosure is a signal processing circuit. Theanalog front-end 410 may further include other circuit units or otherfunction circuits, such as the analog front-end circuit 100 of FIG. 1,but the disclosure is not limited thereto.

Referring to FIG. 2 and FIG. 5A, in the embodiment of the disclosure,the analog front-end circuit 400 may be coupled to the touch panel 210through the panel routing L2, and there is an equivalent capacitance 450between the panel routing L2 and the touch panel 210. One terminal ofthe equivalent capacitance 450 may be coupled to the equivalent resistor440 and the panel routing L2, and another one terminal of the equivalentcapacitance 450 may be coupled to the touch panel 210 through the nodeA5. However, owing to the touch panel 210 is integrated with the displaypanel 220, the analog front-end circuit 400 may also be coupled to thedisplay panel 220 through the panel routing L2, wherein there is anequivalent capacitance 460 between the panel routing L2 and the displaypanel 220. One terminal of the equivalent capacitance 460 may be coupledto the equivalent resistor 440 and the panel routing L2, and another oneterminal of the equivalent capacitance 460 may be coupled to the displaypanel 220 through the node A6. In the embodiment of the disclosure, theanalog front-end 410 is configured to receive the touch driving signalTS from a touch sensor of the touch panel 210 through the panel routingL2 and the first switch 420 to the input terminal of the analogfront-end 410 when the first switch 420 is turned on and the secondswitch 430 is turned off, so that the output terminal of the analogfront-end 410 outputs an output voltage according to the touch drivingsignal TS. Further, the analog front-end circuit 400 is furtherconfigured to transmit a coupling noise signal NS from the display panel220 through the panel routing L2 and the second switch 430 to thereference voltage Vf when the second switch 430 is turned on and thefirst switch 420 is turned off. In other words, the analog front-endcircuit 400 may prevent the analog front-end 410 from receiving thecoupling noise signal NS by controlling the conduction states of thefirst switch 420 and the second switch 430. Furthermore, the thirdswitch 470 is switched synchronously with the second switch 430, and theanalog front-end 410 is reset (or discharged) when the third switch 470is turned on.

FIG. 5B is a schematic diagram illustrating an analog front-end circuitadapted to the self-capacitance touch panel according to anotherembodiment of the disclosure. Referring to FIG. 5B, the analog front-endcircuit 600 may be disposed in a touch controller for sent a touchdriving signal TS to the touch panel 210 of FIG. 2 to sense a sensecapacitance (for example, a self-capacitance) of the touch panel 210,and the touch controller may further include other functional circuits,such as a display driver for driving the display panel 220 of FIG. 2. Inthe embodiment of the disclosure, the analog front-end circuit 600includes an analog front-end 610, a first switch 620, a second switch630 and a third switch 670. In the embodiment of the disclosure, theanalog front end 610 includes a first input terminal, a second inputterminal, and an output terminal. The first input terminal of the analogfront end 610 is coupled to the output terminal of the analog front end610. The first switch 620 includes a first terminal and a secondterminal. The first terminal of the first switch 620 is coupled to thefirst input terminal of the analog front end 610, and the secondterminal of the first switch 620 is coupled to the panel routing L4,where the panel routing L4 has an equivalent resistance 640. The secondswitch 630 includes a first terminal and a second terminal. The firstterminal of the second switch 630 is coupled to the second terminal ofthe first switch 620, and the second terminal of the second switch 630is coupled to the reference voltage Vf1. The third switch 670 includes afirst terminal and a second terminal. The first terminal of the thirdswitch 670 is coupled to the reference voltage Vf2, and the secondterminal of the third switch 670 is coupled to the output terminal ofthe analog front end 610. In the embodiment of the disclosure, the thirdswitch 670 and the second switch 630 are switched synchronously. Inanother embodiment of the disclosure, the reference voltages Vf1 and Vf2may be the touch driving signal TS or the common mode voltage, but thedisclosure is not limited thereto. In addition, the analog front end 610of the disclosure is a signal processing circuit. The analog front end610 may further include other circuit units or other functionalcircuits, such as the analog front end circuit 100 of FIG. 1, but thedisclosure is not limited thereto.

Referring FIG. 2 and FIG. 5B, in the embodiment of the disclosure, theanalog front-end circuit 600 may be coupled to the touch panel 610through the panel routing L4 and the node A7. However, since the touchpanel 210 is integrated with the display panel 220, the analog front-endcircuit 600 may also be coupled to the display panel 220 through thepanel routing L4, where an equivalent capacitance 660 exists between thepanel routing L4 and the display panel 220. One terminal of theequivalent capacitance 660 may be coupled to the equivalent resistor 640and the panel routing L4, and another one terminal of the equivalentcapacitance 660 may be coupled to the display panel 220 through the nodeA8. In the embodiment of the disclosure, the analog front end 610 isconfigured to receive the touch driving signal TS from the second inputterminal of the analog front end 610 when the first switch 620 is turnedon and the second switch 630 is turned off, and then transmit the touchdriving signal TS to the touch sensor of the touch panel 210 through thefirst input terminal of the analog front end 610, the first switch 620,the panel routing L4, and the node A7. The output terminal of the analogfront end 610 outputs the output signal Vout2 according to the touchdriving signal TS induced by the voltage change of self-capacitanceinduction. In addition, the analog front-end circuit 600 is further usedto transmit the coupling noise signal NS from the display panel 220 tothe reference voltage Vf1 through the panel routing L4 and the secondswitch 630 when the second switch 630 is turned on and the first switch620 is turned off. In other words, the analog front-end circuit 600 mayprevent the analog front-end 610 from receiving the coupling noisesignal NS by controlling the conduction state of the first switch 620and the second switch 630. In addition, the third switch 670 is switchedsynchronously with the second switch 630, and the output terminal of theanalog front end 610 may be reset (or discharged) when the third switch670 is turned on.

FIG. 6 is a signal waveform diagram illustrating the operation of theanalog front-end circuit according to another embodiment of thedisclosure. Referring to FIG. 2, FIG. 5 and FIG. 6, in the embodiment ofthe disclosure, the display panel 220 may be driven by a horizontal syncsignal HS, therefore the display panel 220 may synchronously generatethe coupling noise signal NS which is transmitted to the analogfront-end circuit 400. As shown in FIG. 6, each rising edge and eachfalling edge of the coupling noise signal NS may be synchronized witheach rising edge of the horizontal sync signal HS. In the embodiment ofthe disclosure, a signal period of the horizontal sync signal HS issynchronized with an alternating period of each adjacent rising edge andfalling edge of the touch driving signal TS, and the touch drivingsignal TS is shifted to prevent the analog front-end 410 from receivingthe coupling noise signal NS at the same time during the period of theanalog front-end 410 receiving the touch driving signal TS.

In the embodiment of the disclosure, the first switch 420 is configuredto receive a first switching signal S1, the second switch 430 isconfigured to receive a second switching signal S2, and the third switch470 is configured to receive a third switching signal S3. The firstswitching signal S1, the second switching signal S2 and third switchingsignal S3 are periodic square waves, and the first switching signal S1and the second switching signal S2 are inverted. The second switchingsignal S2 and the third switching signal S3 have same waveform. Thus,the second switch 430 and the third switch 470 are turned on duringfirst periods P1, P1′, and the first switch 420 is turned on duringsecond periods P2, P2′. The first period P1 and the second period P2 arenon-overlapping, and the first period P1′ and the second period P2′ arenon-overlapping. It is should be noted that, as shown in FIG. 6 eachfalling edge of the first switching signal S1 is synchronized with theeach rising edge of the horizontal sync signal HS and the each fallingedge and the each rising edge of the coupling noise signal NS, and eachrising edge of the first switching signal S1 is synchronized with eachrising edge and each falling edge of the touch driving signal TS. Thus,each rising edge of each of the second switching signal S2 and the thirdswitching signal S3 is synchronized with the each rising edge of thehorizontal sync signal HS and the each falling edge and the each risingedge of the coupling noise signal NS, and each falling edge of each ofthe second switching signal S2 and the third switching signal S3 issynchronized with the each rising edge and the each falling edge of thetouch driving signal TS. In other words, when the coupling noise signalNS is transmitted through the panel routing L2, the first switch 420 isturned off to prevent the analog front-end 410 from receiving thecoupling noise signal NS.

Therefore, as shown in FIG. 6, the analog front-end circuit 400 mayrelease the coupling noise signal NS through the panel routing 440 andthe second switch 430 to the reference voltage Vf during the firstperiods P1, P1′, and the analog front-end 410 is configured to receivethe touch driving signal TS through the panel routing 440 and the firstswitch 420 during the second period P2. The analog front-end 410 isconfigured to receive the touch driving signal TS without the couplingnoise signal NS or with a relatively low coupling noise signal NS duringthe second period P2, so that the output terminal of the analogfront-end 410 outputs an output signal Vout2 having voltage Vb as shownin FIG. 6 during the second period P2. In the embodiment of thedisclosure, the analog front-end 410 is reset (or discharged) by thethird switch 470 during a next first period P1′, and the analogfront-end 410 may continuously reset (or discharged) during a nextsecond period P2′. It is should be noted that, the output signal Vout2having voltage Vb may represent the touch information of the touchsensor of the touch panel 210, wherein the output signal Vout2 may swingbetween the voltages −Vb to Vb during the periods P1 to P2′. In otherwords, the analog front-end circuit 400 may be operated according to thesignal waveform diagram of FIG. 6, so that the analog front-end circuit400 can output the output signal Vout2 having higher signal-to-noiseratio during the second period P2. In addition, owing to the outputsignal Vout2 may swing between the voltages −Vb to Vb, the output signalVout2 may carry more touch information during the second period P2.

Referring to FIG. 2, FIG. 5B and FIG. 6, the signal waveform of FIG. 6may also be applied to the analog front-end circuit 600 of FIG. 5B. Inthe embodiment of the disclosure, the display panel 220 may be driven bythe horizontal synchronization signal HS, so the display panel 220 maysynchronously generate the coupling noise signal NS which is transmittedto the analog front-end circuit 600. In the embodiment of thedisclosure, when the coupling noise signal NS is transmitted through thepanel routing L4, the first switch 620 is turned off to prevent theanalog front end 610 from receiving the coupling noise signal NS. Asshown in FIG. 6, the analog front end circuit 600 may release thecoupling noise signal NS to the reference voltage Vf1 through the panelrouting L4 and the second switch 630 during the first period P1, P1′,and the second terminal of the analog front end 610 may be used toreceive the touch drive signal TS during the second period P2, so thatthe first output terminal of the analog front end 610 is configured totransmit the touch driving signal TS to the touch panel 210 through thefirst switch 620, the panel wiring L4 and the node A7 during the secondperiod P2.

In the embodiment of the disclosure, during the second period P2, theanalog front end 610 is configured to transmit the touch driving signalTS without receiving the coupling noise signal NS or receiving arelatively low coupling noise signal NS to the touch panel 210 forsensing, so that the output terminal of the analog front end 610 outputsthe output signal Vout2 having the voltage Vb during the second periodP2. In the embodiment of the disclosure, the analog front end 610 isreset (or discharged) by the third switch 670 during the next firstperiod P1′, and the analog front end 610 may be continuously reset (ordischarged) during the next second period P2′. It should be noted that,the output signal Vout2 having the voltage Vb may represent the touchinformation of the touch sensor of the touch panel 210, where the outputsignal Vout2 may swing from the voltage −Vb to the voltage Vb during theperiod P1 to the period P2′. In other words, the analog front-endcircuit 600 may be operated according to the signal waveform diagram ofFIG. 6, so that the analog front-end circuit 600 may output the outputsignal Vout2 with a higher signal-to-noise ratio during the secondperiod P2. In addition, during the second period P2, since the outputsignal Vout2 may swing from the voltage −Vb to the voltage Vb, theoutput signal Vout2 may carry more touch information. The voltage Vb is,for example, less than the power supply voltage VDD, and the voltage −Vbis, for example, greater than the power supply voltage −VDD.

However, regarding the signal waveform characteristics of thisembodiment (FIG. 5B and FIG. 6), please refer to the above embodiment(FIG. 5A and FIG. 6) to obtain sufficient teaching, suggestion, andimplementation description, so there will not repeat again. In addition,FIG. 5A and FIG. 5B may have different voltage oscillations when thesignal waveform of FIG. 6 is applied. The signal waveform of FIG. 6 isonly used to show the relationships between the switching result of eachswitch and the change of each signal waveform, and do not limit theanalog front-end circuits 400 and 600 of FIG. 5A and FIG. 5B to operatewith the same voltage amplitude results.

FIG. 7 is a signal waveform diagram illustrating the operation of theanalog front-end circuit according to yet another embodiment of thedisclosure. Referring to FIG. 2, FIG. 5A and FIG. 7, the signal waveformof FIG. 7 may be applied to the analog front-end circuit 400 of FIG. 5A.In the embodiment of the disclosure, the analog front-end circuit 400may be act in concert with the multiplexers 221, 222. In the embodimentof the disclosure, the display panel 220 may be driven by a horizontalsync signal HS. The multiplexer 221 may be controlled by a multiplexercontrol signal MS1, and the multiplexer 222 may be controlled by amultiplexer control signal MS2. The multiplexer 221 may be controlled bya multiplexer control signal MS1, and the multiplexer 222 may becontrolled by a multiplexer control signal MS2. The multiplexer controlsignals MS1, MS2 are periodic square waves, and multiplexer controlsignals MS1, MS2 are inverted. Therefore, as shown in FIG. 7, inresponse to the horizontal sync signal HS and the switching operation ofthe multiplexers 221, 222, the display panel 220 may synchronouslygenerate the coupling noise signal NS to the analog front-end circuit400. In other words, the coupling noise signal NS may include noisesfrom the switching operation of the multiplexers 221, 222. As shown inFIG. 7, each rising edge and each falling edge of the coupling noisesignal NS may be synchronized with each rising edge and each fallingedge of the multiplexer control signals MS1, MS2. In the embodiment ofthe disclosure, a signal period of the horizontal sync signal HS may besynchronized with a signal period of the touch driving signal TS, andthe touch driving signal TS be shifted to prevent the analog front-end410 from receiving the coupling noise signal NS during the period of theanalog front-end 410 receiving the touch driving signal TS.

In the embodiment of the disclosure, the first switch 420 is configuredto receive a first switching signal S1, the second switch 430 isconfigured to receive a second switching signal S2, and the third switch430 is configured to receive a third switching signal S3. The firstswitching signal S1, the second switching signal S2 and third switchingsignal S3 are periodic square waves, and the first switching signal S1and the second switching signal S2 are inverted. The second switchingsignal S2 and the third switching signal S3 have same waveform. Thus,the second switch 430 and the third switch 470 are turned on duringfirst periods P1, P1′, and the first switch 420 is turned on duringsecond periods P2, P2′. The first periods P1, P1′ and the second periodsP2, P2′ are non-overlapping. It is should be noted that, as shown inFIG. 7, each interval falling edge of the first switching signal S1 issynchronized with each rising edge of the horizontal sync signal HS, andeach rising edge of the first switching signal S1 is synchronized withthe each rising edge and each falling edge of the touch driving signalTS. Further, the each falling edge of the first switching signal S1 issynchronized with each falling edge and each rising edge of themultiplexer control signals MS1, MS2 and the coupling noise signal NS.Thus, each interval rising edge of the second switching signal S2 andthe third switching signal S3 is synchronized with the each rising edgeof the horizontal sync signal HS, and each falling edge of the secondswitching signal S2 and the third switching signal S3 is synchronizedwith the each rising edge and the each falling edge of the touch drivingsignal TS. Further, the each rising edge of the second switching signalS2 and the third switching signal S3 is synchronized with the eachrising edge and the each falling edge of the multiplexer control signalsMS1, MS2 and the coupling noise signal NS. In other words, when thecoupling noise signal NS is transmitted through the panel routing L2,the first switch 420 is turned off to prevent the analog front-end 410from receiving the coupling noise signal NS.

Therefore, as shown in FIG. 7, the analog front-end circuit 400 mayrelease the coupling noise signal NS through the panel routing 440 andthe second switch 430 to the reference voltage Vf during the firstperiods P1, P1′, and the analog front-end 410 is configured to receivethe touch driving signal TS through the panel routing 440 and the firstswitch 420 during the second period P2. The analog front-end 410 isconfigured to receive the touch driving signal TS without the couplingnoise signal NS or with a relatively low coupling noise signal NS duringthe second period P2, so that the output terminal of the analogfront-end 410 outputs an output signal Vout2 having voltage Vb as shownin FIG. 7 during the second period P2. In the embodiment of thedisclosure, the analog front-end 410 is reset (or discharged) by thethird switch 470 during a next first period P1′, and the analogfront-end 410 may continuously reset (or discharged) during a nextsecond period P2′. It is should be noted that, the output signal Vout2having voltage Vb may represent the touch information of the touchsensor of the touch panel 210, wherein the output signal Vout2 may swingbetween the voltages −Vb to Vb. In other words, the analog front-endcircuit 400 may be operated according to the signal waveform diagram ofFIG. 7, so that the analog front-end circuit 400 can output the outputsignal Vout2 having higher signal-to-noise ratio during the secondperiod P2. In addition, owing to the output signal Vout2 may swingbetween the voltages −Vb to Vb, the output signal Vout2 may carry moretouch information during the second period P2.

Referring to FIG. 2, FIG. 5B and FIG. 7, the signal waveform of FIG. 7may be applied to the analog front-end circuit 600 of FIG. 5B. In theembodiment of the disclosure, the analog front-end circuit 600 may actin concert with the multiplexers 221 and 222. In the embodiment of thedisclosure, the display panel 220 may be driven by the horizontalsynchronization signal HS. The multiplexer 221 may be controlled by themultiplexer control signal MS1, and the multiplexer 222 may becontrolled by the multiplexer control signal MS2. In the embodiment ofthe disclosure, in response to the horizontal synchronization signal HSand the switching operations of the multiplexers 221 and 222, thedisplay panel 220 may synchronously generate the coupling noise signalNS which is transmitted to the analog front-end circuit 600. In otherwords, the coupling noise signal NS may include noise from the switchingoperations of the multiplexers 221 and 222. In the embodiment of thedisclosure, when the coupling noise signal NS is transmitted through thepanel wiring L2, the first switch 620 is turned off to prevent theanalog front end 610 from receiving the coupling noise signal NS.

In the embodiment of the disclosure, the first end of the analog frontend 610 is used to transmit the driving signal TS to the touch panel 210for sensing during the second period P2 without receiving the couplingnoise signal NS or receiving a relatively low coupling noise signal NS,so that the output terminal of the analog front end 610 outputs theoutput signal Vout2 having the voltage Vb during the second period P2.In the embodiment of the disclosure, the analog front end 610 is reset(or discharged) by the third switch 670 during the next first periodP1′, and the analog front end 610 may be continuously reset (ordischarged) during the next second period P2′. It should be noted that,the output signal Vout2 having the voltage Vb may represent the touchinformation of the touch sensor of the touch panel 210, where the outputsignal Vout2 may swing from the voltage −Vb to the voltage Vb. In otherwords, the analog front-end circuit 600 may operate according to thesignal waveform diagram of FIG. 7, so that the analog front-end circuit600 may output the output signal Vout2 with a higher signal-to-noiseratio during the second period P2. In addition, during the second periodP2, since the output signal Vout2 may swing from the voltage −Vb to thevoltage Vb, the output signal Vout2 may carry more touch information.

However, regarding the signal waveform characteristics of thisembodiment (FIG. 5B and FIG. 7), please refer to the above-mentionedembodiment (FIG. 5A and FIG. 7) to obtain sufficient teaching,suggestion, and implementation description, so there will not repeatagain. In addition, FIG. 5A and FIG. 5B may have different voltageoscillations when the signal waveform of FIG. 7 is applied. The signalwaveform of FIG. 7 is only used to show the relationships between theswitching results of each off and on and the change of each signalwaveform. It is not a limitation that the analog front-end circuits 400and 600 of FIG. 5A and FIG. 5B use the same voltage amplitude result tooperate.

FIG. 8 is a signal waveform diagram illustrating the operation of theanalog front-end circuit according to yet again another embodiment ofthe disclosure. Referring to FIG. 2, FIG. 5A and FIG. 8, in theembodiment of the disclosure, the analog front-end circuit 400 may beact in concert with the transistor 232 of FIG. 2 receiving the emissionsignal ES. In the embodiment of the disclosure, the pixel unit 230 maybe driven by the emission signal ES. It is should be noted that, owingto a frame rate of touch panel 210 is higher than a frame rate of thedisplay panel 220, one signal period of the emission signal ES is longerthan one signal period of the touch driving signal TS. Therefore, asshown in FIG. 8, in response to the emission signal ES, the displaypanel 220 may synchronously generate the coupling noise signal NS to theanalog front-end circuit 400. In other words, the coupling noise signalNS may include noises from the driven operation of the pixel unit 230.As shown in FIG. 8, each rising edge and each falling edge of thecoupling noise signal NS may be synchronized with each rising edge andeach falling edge of the emission signal ES. In the embodiment of thedisclosure, a signal period of the emission signal ES may besynchronized with N times of a signal period of the touch driving signalTS, and the waveform of the touch driving signal TS may be shifted toprevent the analog front-end 410 from receiving the coupling noisesignal NS during the period of the analog front-end 410 receiving thetouch driving signal TS, wherein N is a positive integer.

In the embodiment of the disclosure, the first switch 420 is configuredto receive a first switching signal S1, the second switch 430 isconfigured to receive a second switching signal S2, and the third switch470 is configured to receive a third switching signal S3. The firstswitching signal S1, the second switching signal S2 and third switchingsignal S3 are periodic square waves, and the first switching signal S1and the second switching signal S2 are inverted. The second switchingsignal S2 and the third switching signal S3 have same waveform. Thus,the second switch 430 and the third switch 470 are turned on duringfirst periods P1, P1′, and the first switch 420 and the third switch 470are turned on during second periods (similar to the second periods P2,P2′ of FIG. 6 or FIG. 7). The first periods P1, P1′ and the above secondperiods are non-overlapping. It is should be noted that, as shown inFIG. 7, each N-th falling edge of the first switching signal S1 issynchronized with the each falling edge and the each rising edge of theemission signal ES and the coupling noise signal NS, and each risingedges of the first switching signal S1 is synchronized with each fallingedge and each rising edge of the touch driving signal TS, where N is apositive integer. Thus, each N-th rising edge of each of the secondswitching signal S2 and the third switching signal S3 is synchronizedwith the each falling edge and the each rising edge of the emissionsignal ES and the coupling noise signal NS, and each rising edge of eachof the second switching signal S2 and the third switching signal S3 issynchronized with the each falling edge and the each rising edge of thetouch driving signal TS. In other words, when the coupling noise signalNS is transmitted through the panel routing L2, the first switch 420 isturned off to prevent the analog front-end 410 from receiving thecoupling noise signal NS.

Therefore, as shown in FIG. 8, the analog front-end circuit 400 mayrelease the coupling noise signal NS through the panel routing 440 andthe second switch 430 to the reference voltage Vf during the firstperiods P1, P1′, and the analog front-end 410 is configured to receivethe touch driving signal TS through the panel routing 440 and the firstswitch 420 during the second period (similar to the second period P2 ofFIG. 6 or FIG. 7). The analog front-end 410 is configured to receive thetouch driving signal TS without the coupling noise signal NS or with arelatively low coupling noise signal NS during the second period(similar to the second period P2 of FIG. 6 or FIG. 7), so that theoutput terminal of the analog front-end 410 outputs an output signalVout2 having voltage Vb as shown in FIG. 8 during the second period(similar to the second period P2 of FIG. 6 or FIG. 7). In the embodimentof the disclosure, the analog front-end 410 is reset (or discharged) bythe third switch 470 during a next first period P1′, and the analogfront-end 410 may continuously reset (or discharged) during a nextsecond period (similar to the second period P2′ of FIG. 6 or FIG. 7). Itis should be noted that, the output signal Vout2 having voltage Vb mayrepresent the touch information of the touch sensor of the touch panel210, wherein the output signal Vout2 may swing between the voltages −Vbto Vb. In other words, the analog front-end circuit 400 may be operatedaccording to the signal waveform diagram of FIG. 8, so that the analogfront-end circuit 400 can output the output signal Vout2 having highersignal-to-noise ratio during the second period P2 (similar to the secondperiod P2 of FIG. 6 or FIG. 7). In addition, owing to the output signalVout2 may swing between the voltages −Vb to Vb, the output signal Vout2may carry more touch information during the second period P2.

Referring to FIG. 2, FIG. 5B and FIG. 8, the signal waveform of FIG. 8may also be applied to the analog front-end circuit 600 of FIG. 5B. Inthe embodiment of the disclosure, the analog front-end circuit 600 mayact in concert with the transistor 232 for receiving the emission signalES. In the embodiment of the disclosure, the pixel unit 230 may bedriven by the emission signal ES. It should be noted that, since theimage update rate of the touch panel 210 is higher than the image updaterate of the display panel 220, one signal period of the emission signalES is longer than one signal period of the touch drive signal TS. In theembodiment of the disclosure, in response to the emission signal ES, thedisplay panel 220 may synchronously generate the coupling noise signalNS which is transmitted to the analog front-end circuit 600. In otherwords, the coupling noise signal NS may include noise from the drivingoperation of the pixel unit 230. In the embodiment of the disclosure,when the coupling noise signal NS is transmitted through the panelwiring L4, the first switch 620 is turned off to prevent the analogfront end 610 from receiving the coupling noise signal NS.

In the embodiment of the disclosure, the first end of the analog frontend 610 is used to transmit the touch driving signal TS to the touchpanel 210 for sensing during the second period (similar to the secondperiod P2 shown in FIG. 6 or FIG. 7) without receiving the couplingnoise signal NS or receiving relatively low coupling noise signal NS, sothat the output terminal of the analog front end 610 outputs an outputsignal Vout2 having a voltage Vb during the second period (similar tothe second period P2 shown in FIG. 6 or FIG. 7). In the embodiment ofthe disclosure, the analog front end 410 is reset (or discharged)through the third switch 470 during the next first period P1′, and maybe reset (or discharged) in the next second period (similar to thesecond period P2′ shown in FIG. 6 or FIG. 7), the analog front end 410is continuously reset (or discharged). It should be noted that, theoutput signal Vout2 having the voltage Vb may represent the touchinformation of the touch sensor of the touch panel 210, where the outputsignal Vout2 may swing from the voltage −Vb to the voltage Vb. In otherwords, the analog front-end circuit 600 may operate according to thesignal waveform diagram of FIG. 8, so that during the second period P2(similar to the second period P2′ shown in FIG. 6 or FIG. 7), the outputof the analog front-end circuit 600 may be higher than the output signalVout2 of the signal-to-noise ratio. In addition, during the secondperiod P2, since the output signal Vout2 may swing from the voltage −Vbto the voltage Vb, the output signal Vout2 may carry more touchinformation.

However, regarding the signal waveform characteristics of thisembodiment (FIG. 5B and FIG. 8), please refer to the above-mentionedembodiment (FIG. 5A and FIG. 8) to obtain sufficient teaching,suggestion, and implementation description, so there will not repeatagain. In addition, the embodiments of FIG. 5A and FIG. 5B may havedifferent voltage vibrations when the signal waveform of FIG. 8 isapplied. The signal waveform of FIG. 8 is only used to show therelationships between the switching results of each off and on and thechange of each signal waveform. It is not a limitation that, the analogfront-end circuits 400 and 600 of FIG. 5A and FIG. 5B use the samevoltage amplitude result to operate.

It is should be noted that, in some embodiments of the disclosure, thesignal waveform diagrams of FIG. 7 and FIG. 8 may also be applied to theanalog front-end circuit 300 of FIG. 3A and FIG. 3B except for thesignal waveform of the third switching signal S3. Moreover, based on theteachings of embodiments of FIG. 4, FIG. 6 to FIG. 8, in another someembodiments of the disclosure, the switches in the analog front-endcircuit 300 and 500 of FIG. 3A and FIG. 3B or the analog front-endcircuit 400 and 600 of FIG. 5A and FIG. 5B may also be act in concertwith the horizontal sync signal, the multiplexers and the transistorreceiving the emission signal synchronously.

FIG. 9 is a flowchart of an operating method according to an embodimentof the disclosure. Referring to FIG. 2, FIG. 3A and FIG. 9, theoperating method of the embodiment may be adapted to the analogfront-end circuit 300, 400, 500 or 600 of FIG. 3A, FIG. 3B, FIG. 5A orFIG. 5B. However, the following description uses the analog front-endcircuit 300 of FIG. 3A as an example. In step S910, the analog front-endcircuit 300 turns on the second switch 330 during the first period. Instep S920, the coupling noise signal NS from the display panel 220 istransmitted through the panel routing L1 and the second switch 330 tothe reference voltage Vf during the first period. In step S930, theanalog front-end circuit 300 turns on the first switch 320 during asecond period. In step S940, the input terminal of the analog front-end310 receives a touch driving signal TS during the second period. In theembodiment of the disclosure, the first period and the second period arenon-overlapping. Therefore, the analog front-end circuit 300 performingstep S910 to S940 may prevent the analog front-end 310 from receivingthe coupling noise signal NS by controlling the conduction states of thefirst switch 320 and the second switch 330.

In addition, the relevant circuit features, implementation details, andrelated technical features of the analog front-end circuit 300 mayobtain sufficient teachings, suggestions, and implementationdescriptions based on the description of the above-mentioned embodimentsof FIG. 1 to FIG. 8, and there will not repeat again. Furthermore, it issimilar to the above description using FIG. 3A as the example, the abovesteps S910 to S940 can also be applied to be executed by the analogfront-end circuits 400, 500, and 600 of FIG. 3B, FIG. 5A, and FIG. 5B,and there will not be repeat again.

In summary, according to the analog front-end circuit for the touchcontroller and the operating method thereof of the disclosure, bycontrolling the conduction states of the switches disposed between thepanel routing and the analog front-end, the analog front-end circuit caneffectively avoid to receive the noise signal generated by the displaypanel when the analog front-end circuit receives the touch drivingsignal. Moreover, in some embodiments of the disclosure, the outputsignal of the analog front-end circuit may further has a wide voltageswing so as to carry more touch information.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed embodimentswithout departing from the scope or spirit of the disclosure. In view ofthe foregoing, it is intended that the disclosure covers modificationsand variations provided that they fall within the scope of the followingclaims and their equivalents.

What is claimed is:
 1. An analog front-end circuit for a touchcontroller, comprising: an analog front-end, comprising an inputterminal and an output terminal; a first switch, comprising a firstterminal and a second terminal, wherein the first terminal of the firstswitch is coupled to the input terminal of the analog front-end, and thesecond terminal of the first switch is configured to receive a touchdriving signal from a panel routing; and a second switch, comprising afirst terminal and a second terminal, wherein the first terminal of thesecond switch is coupled to the second terminal of the first switch, andthe second terminal of the second switch is coupled to a referencevoltage, wherein the first switch is configured to receive a firstswitching signal to turn on the first switch, and the second switch isconfigured to receive a second switching signal to turn on the secondswitch, wherein the first switching signal and the second switchingsignal are periodic square waves, and the first switching signal and thesecond switching signal are inverted.
 2. The analog front-end circuitaccording to the claim 1, wherein the second switch is turned on duringa first period, and the first switch is turned on during a secondperiod, wherein the first period and the second period arenon-overlapping.
 3. The analog front-end circuit according to the claim1, wherein the panel routing is further coupled to a touch panel and adisplay panel, and the input terminal of the analog front-end receivesthe touch driving signal of the touch panel through the panel routingand the first switch during the second period.
 4. The analog front-endcircuit according to the claim 3, wherein the display panel is a microLED display.
 5. The analog front-end circuit according to the claim 3,wherein the touch panel is a mutual capacitance touch panel or aself-capacitance touch panel.
 6. The analog front-end circuit accordingto the claim 3, wherein an alternating period of each adjacent risingedge and falling edge of the touch driving signal are synchronized witha signal period of a horizontal sync signal of the display panel.
 7. Theanalog front-end circuit according to the claim 6, wherein each fallingedge of the first switching signal is synchronized with each rising edgeof the horizontal sync signal.
 8. The analog front-end circuit accordingto the claim 3, wherein each rising edge of the first switching signalis synchronized with each rising edge and each falling edge of the touchdriving signal.
 9. The analog front-end circuit according to the claim3, wherein a couple noise signal from the display panel is transmittedthrough the panel routing and the second switch to the reference voltageduring the first period.
 10. The analog front-end circuit according tothe claim 9, wherein each falling edge of the first switching signal issynchronized with each rising edge and each falling edge of the couplingnoise signal of the display panel.
 11. The analog front-end circuitaccording to the claim 3, wherein a signal period of the touch drivingsignal is equal to a signal period of a horizontal sync signal of thedisplay panel.
 12. The analog front-end circuit according to the claim3, wherein each falling edge of the first switching signal issynchronized with each rising edge and each falling edge of amultiplexer control signal of the display panel.
 13. The analogfront-end circuit according to the claim 3, wherein N times of a signalperiod of the touch driving signal is equal to a signal period of anemission signal of the display panel, wherein N is a positive integer.14. The analog front-end circuit according to the claim 11 wherein eachN-th falling edge of the first switching signal is synchronized witheach falling edge and each rising edge of the emission signal.
 15. Theanalog front-end circuit according to the claim 3, wherein the inputterminal of the analog front-end receives the touch driving signal ofthe touch panel through the panel routing and the first switch duringthe second period.
 16. The analog front-end circuit according to theclaim 3, wherein the input terminal of the analog front-end comprises afirst input terminal and a second input terminal, wherein the secondinput terminal of the analog front end receives the touch driving signalduring the second period, and the first input terminal of the analogfront end sends the touch driving signal to the touch panel through thepanel routing and the first switch during the second period.
 17. Theanalog front-end circuit according to the claim 1, further comprising: athird switch, comprising a first terminal and a second terminal, whereinthe first terminal of the third switch is coupled to the input terminalof the analog front-end and the second terminal of the third switch iscoupled to the output terminal of the analog front-end, wherein thethird switch is switched synchronously with the second switch.
 18. Theanalog front-end circuit according to the claim 1, further comprising: athird switch, comprising a first terminal and a second terminal, whereinthe first terminal of the third switch is coupled to another referencevoltage and the second terminal of the third switch is coupled to theoutput terminal of the analog front end, wherein the third switch andthe second switch are switched synchronously.
 19. The analog front-endcircuit according to the claim 1, wherein the reference voltage is acommon mode voltage or the touch driving signal.
 20. An operating methodof an analog front-end circuit for a touch controller, wherein theanalog front-end circuit comprises an analog front-end, a first switchand a second switch, an input terminal of the analog front-end iscoupled to a first terminal of the first switch, a second terminal ofthe first switch is coupled to a panel routing and a first terminal ofthe second switch, a second terminal of the second switch is coupled toa reference voltage, and the panel routing is further coupled to a touchpanel and a display panel, wherein the operating method comprises:receiving, by the first switch, a first switching signal; receiving, bythe second switch, a second switching signal, wherein the firstswitching signal and the second switching signal are periodic squarewaves, and the first switching signal and the second switching signalare inverted; transmitting a coupling noise signal from the displaypanel through the panel routing and the second switch to the referencevoltage when the second switch is turned on by a second switchingsignal; and receiving a touch driving signal by the input terminal ofthe analog front-end through the panel routing and the first switch whenthe first switch is turned on by a first switching signal.
 21. Theoperating method according to the claim 20, wherein an alternatingperiod of each adjacent rising edge and falling edge of the touchdriving signal are synchronized with a signal period of a horizontalsync signal of the display panel.
 22. The operating method according tothe claim 21, wherein each falling edge of the first switching signal issynchronized with each rising edge of the horizontal sync signal. 23.The operating method according to the claim 20, wherein each rising edgeof the first switching signal is synchronized with each rising edge andeach falling edge of the transmitter driving signal.
 24. The operatingmethod according to the claim 20, wherein each falling edge of the firstswitching signal is synchronized with each rising edge and each fallingedge of the coupling noise signal of the display panel.
 25. Theoperating method according to the claim 20, wherein a signal period ofthe touch driving signal is equal to a signal period of a horizontalsync signal of the display panel.
 26. The operating method according tothe claim 20, wherein a falling edge of the first switching signal issynchronized with each rising edge and each falling edge of amultiplexer control signal of the display panel.
 27. The operatingmethod according to the claim 20, wherein N times of a signal period ofthe touch driving signal is equal to a signal period of an emissionsignal of the display panel, wherein N is a positive integer.
 28. Theoperating method according to the claim 27, wherein each N-th fallingedge of the first switching signal is synchronized with each fallingedge and each rising edge of the emission signal.
 29. The operatingmethod according to the claim 20, wherein the analog front-end circuitfurther comprises a third switch, and a first terminal of the thirdswitch is coupled to the input terminal of the analog front-end, and asecond terminal of the third switch is coupled to the output terminal ofthe analog front-end, wherein the third switch is switched synchronouslywith the second switch.
 30. The operating method according to the claim20, wherein the reference voltage is a common mode voltage or the touchdriving signal.
 31. The operating method according to the claim 20,wherein the input terminal of the analog front-end comprises a firstinput terminal and a second input terminal, and the step of receivingthe touch driving signal by the input terminal of the analog front-endcomprises: receiving the touch driving signal by the second inputterminal of the analog front end during the second period, and sendingthe touch driving signal to the touch panel by the first input terminalof the analog front end through the first switch and the panel routingduring the second period.